Markdown: Use different background color for code

Sets the background color for code blocks and for inline code (actually
for any fixed font text).

Change-Id: I1365111b38314a8e0a129aca35d754ad3f2f13bb
Reviewed-by: Cristian Adam <cristian.adam@qt.io>

src/libs/utils/stringutils.cpp

@@ -5,6 +5,7 @@
 
 #include "filepath.h"
 #include "qtcassert.h"
+#include "stylehelper.h"
 #include "theme/theme.h"
 #include "utilstr.h"
 
@@ -18,6 +19,7 @@
 #include <QJsonArray>
 #include <QJsonValue>
 #include <QLocale>
+#include <QPalette>
 #include <QRegularExpression>
 #include <QSet>
 #include <QTextDocument>
@@ -573,16 +575,28 @@ QTCREATOR_UTILS_EXPORT int endOfNextWord(const QString &string, int position)
 MarkdownHighlighter::MarkdownHighlighter(QTextDocument *parent)
     : QSyntaxHighlighter(parent)
     , h2Brush(Qt::NoBrush)
+    , m_codeBgBrush(Qt::NoBrush)
 {
     parent->setIndentWidth(30); // default value is 40
 }
 
+QBrush MarkdownHighlighter::codeBgBrush()
+{
+    if (m_codeBgBrush.style() == Qt::NoBrush) {
+        m_codeBgBrush = StyleHelper::mergedColors(QGuiApplication::palette().color(QPalette::Text),
+                                                  QGuiApplication::palette().color(QPalette::Base),
+                                                  10);
+    }
+    return m_codeBgBrush;
+}
+
 void MarkdownHighlighter::highlightBlock(const QString &text)
 {
     if (text.isEmpty())
         return;
 
-    QTextBlockFormat fmt = currentBlock().blockFormat();
+    const QTextBlock block = currentBlock();
+    QTextBlockFormat fmt = block.blockFormat();
     QTextCursor cur(currentBlock());
     if (fmt.hasProperty(QTextFormat::HeadingLevel)) {
         fmt.setTopMargin(10);
@@ -610,7 +624,8 @@ void MarkdownHighlighter::highlightBlock(const QString &text)
         }
         cur.setBlockFormat(fmt);
     } else if (fmt.hasProperty(QTextFormat::BlockCodeLanguage) && fmt.indent() == 0) {
-        // set identation for code blocks
+        // set identation and background for code blocks
+        fmt.setBackground(codeBgBrush());
         fmt.setIndent(1);
         cur.setBlockFormat(fmt);
     }
@@ -624,6 +639,16 @@ void MarkdownHighlighter::highlightBlock(const QString &text)
             list->setFormat(listFmt);
         }
     }
+
+    // background color of code
+    for (auto it = block.begin(); it != block.end(); ++it) {
+        const QTextFragment fragment = it.fragment();
+        QTextCharFormat fmt = fragment.charFormat();
+        if (fmt.fontFixedPitch()) {
+            fmt.setBackground(codeBgBrush());
+            setFormat(fragment.position() - block.position(), fragment.length(), fmt);
+        }
+    }
 }
 
 } // namespace Utils

src/libs/utils/stringutils.h

@@ -130,7 +130,10 @@ public:
     void highlightBlock(const QString &text);
 
 private:
+    QBrush codeBgBrush();
+
     QBrush h2Brush;
+    QBrush m_codeBgBrush;
 };
 
 } // namespace Utils